1. Field of the Invention The present invention relates generally to medical methods and apparatus. More particularly, the present invention relates to methods for selectively ablating target sites in the lung while protecting adjacent lung and tissue structures.
Chronic obstructive pulmonary disease is a significant medical problem affecting 16 million people or about 6% of the U.S. population. Specific diseases in this group include chronic bronchitis and emphysema. Emphysema is a condition of the lung characterized by the abnormal permanent enlargement of the airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls, and without obvious fibrosis. It is known that emphysema and other pulmonary diseases reduce the ability of one or both lungs to fully expel air during the exhalation phase of the breathing cycle. One of the effects of such diseases is that the diseased lung tissue is less elastic than healthy lung tissue, which is one factor that prevents full exhalation of air. During breathing, the diseased portion of the lung does not fully recoil due to the emphysematic lung tissue being less elastic than healthy tissue. Consequently, the diseased lung tissue exerts a relatively low driving force, which results in the diseased lung expelling less air volume than a healthy lung. The reduced air volume exerts less force on the airway, which allows the airway to close before all air has been expelled (air trapping), another factor that prevents full exhalation. While a number of therapeutic interventions are used and have been proposed, none are completely effective, and chronic obstructive pulmonary disease remains the fourth most common cause of death in the United States. Thus, improved and alternative treatments and therapies would be of significant benefit.
Of particular interest to the present invention, lung function in patients suffering from emphysema and other chronic obstructive pulmonary diseases can be improved by reducing the effective lung volume, typically by resecting or otherwise isolating diseased portions of the lung. Resection of diseased portions of the lungs both promotes expansion of the non-diseased regions of the lung and decreases the portion of inhaled air which goes into the lungs but is unable to transfer oxygen to the blood. Lung reduction is conventionally performed in open chest or thoracoscopic procedures where part of the lung is resected, typically using stapling devices having integral cutting blades.
While effective in many cases, conventional lung reduction surgery is significantly traumatic to the patient, even when thoracoscopic procedures are employed. Such procedures often result in the unintentional removal of healthy lung tissue, and frequently leave perforations or other discontinuities in the lung which result in air leakage from the remaining lung. Even technically successful procedures can cause respiratory failure, pneumonia, death, and many older or compromised patients are not even candidates for these procedures.
The use of devices that intrathoracically isolate a diseased region of the lung in order to reduce the volume of the diseased region, such as by collapsing the diseased lung region, has recently been proposed. For example, self-expanding plugs, one-way valves, and other occlusion devices may be implanted in airways feeding a targeted region of the lung to isolate the region of the diseased lung region. However, even with the implanted isolation devices properly deployed, air can flow into the isolated lung region via a collateral pathway. This can result in the diseased region of the lung still receiving air even though the isolation devices were implanted into the direct pathways to the lung. Collateral flow can be, for example, air flow that flows between segments of a lung (intralobar collateral ventilation), or it can be, for example, air flow that flows between lobes of a lung (interlobar collateral ventilation). Collateral resistance is reduced in emphysema, and may be substantially lower than airway resistance. Fissures are often incomplete, allowing collateral ventilation to traverse lobes. It is axiomatic that absorptive atelectasis could not develop in patients after the occlusive devices were placed if occluded regions received more ventilation than the rate of gas absorption. Collateral channels were the only pathways available for such ventilation.
For these reasons, it would be desirable to provide improved methods, apparatus, and systems for treating diseased lung regions. In particular, it would be desirable to provide such methods, apparatus, and systems which are capable of treating diseased regions having collateral ventilation using principally or only intrabronchial access routes. It would be still further desirable if the present invention could provide for complete isolation of the diseased lung region while minimizing or eliminating any risk of injury or trauma to adjacent lung or other tissue structures. At least some of these objectives will be met by the inventions described hereinbelow.